Diabetes mellitus has emerged as a pressing global public health concern in the 21st century, necessitating the exploration of effective and safer therapeutic alternatives to conventional synthetic anti-diabetic medications. This study aimed to comprehensively evaluate the anti-diabetic potential of Castanopsis tribuloides through a multi-faceted approach encompassing in vitro, in vivo, and in silico experiments. In vitro assessments revealed that the methanol extract of C. tribuloides bark (CtbME) exhibited remarkable α-glucosidase inhibitory activity, as demonstrated by a low IC50 value of 550 μg/mL, surpassing that of acarbose (600 μg/mL). Furthermore, CtbME administration led to a significant and dose-dependent reduction in hyperglycemic blood glucose levels. Twenty-three secondary metabolites were identified in GC-MS analysis. Molecular docking analysis was employed to elucidate the molecular interactions between C. tribuloides constituents and α-glucosidase. Rutin hydrate, catechin hydrate, and betulin exhibited higher binding affinity than acarbose, where rutin hydrate demonstrated exceptional stability throughout molecular dynamics simulation (MDS), affirming the accuracy of the docking data. The findings of this research underscore the potential of C. tribuloides as a source of anti-diabetic agents and provide valuable insights into the molecular mechanisms underlying its efficacy.